Certain types of human activities benefit from having a media accompaniment and, in particular, a musical accompaniment. Examples of such activities include dance lessons, aerobics, and social events. At present, there are two alternative ways to provide such an accompaniment: live performance, and played-back, pre-recorded media.
Both currently existing methods have their disadvantages. Live performance has three main problems: high costs, limited repertoire and imperfect quality. First, human labor is typically more expensive than using machines; in particular, employing performers is significantly more costly than using pre-recorded media. Furthermore, the memory capacity of an average person is by far more limited than that of a computer: For example, a typical classical pianist is able to play a few dozen musical pieces by heart, while a leading classical music database, such as the Naxos Music Library (http://www.naxosmusiclibrary.com), contains over a million of recorded tracks. Finally, in many cases the limited repertoire of performers does not meet the real-time requirements of the activity, forcing the performer to improvise. The result is usually an inferior quality of the accompaniment, compared to well-rehearsed and polished material composed by great masters. This problem is particularly acute in classical ballet accompaniment.
The central problem of using pre-recorded media is the lack of real-time flexibility and responsiveness. With live performance, it is typically possible to spontaneously set requirements on the fly. For instance, one can ask a musician to switch to another style or to perform a specific composition. To achieve a similar flexibility when using pre-recorded media, extensive time-consuming preparations are required. These include meticulous planning of all possible scenarios the activity can turn to, searching for and choosing the most appropriate media files, acquiring them, editing them if necessary, transferring them into a playable format and, finally, validating their quality and applicability for the activity. Thus, for an hour-long activity the preparations can easily take double or triple the time. Moreover, even after these lengthy preparations, using the final product of these efforts in real-time still requires the constant attention of the person running the activity.